The invention concerns transesterification catalysts and more particular phosphonium phenolate catalysts
The production of phosphonium phenolates is known from DE 197 27 351 C1 and WO 01 46100 A. Processes for the synthesis of highly pure phosphonium phenolates, which are obtained as phenol adducts in crystalline form, are described therein. The phenol adducts of phosphonium phenolates thus obtained are used inter alia as interesterification catalysts in melt interesterification processes for the production of polycarbonate. For use in these melt interesterification processes the purity of the catalysts plays a decisive role, since impurities may lead to activity fluctuations, discoloration or secondary reactions in the interesterification process. As a rule, however, the production of phenol adducts of phosphonium phenolates is not linked either physically or in terms of apparatus to the interesterification process. That means that the catalyst has to be stored until it is used. Depending on the storage conditions, however, the purity of the catalysts and hence the quality of the end product to be obtained may deteriorate. This is commonly being compensated for by the addition of alkaline co-catalysts, such as sodium phenolate for example. The prior art contains no mention of how this problem might be overcome, however.
On the basis of the prior art the object thus arises of finding a process for the storage of phosphonium phenolates that guarantees a constant catalyst quality. Surprisingly it has now been found that storage is possible if certain parameters are maintained.
The present invention therefore provides the storage of phenol adducts of phosphonium phenolates as a crystalline solid by keeping them at a certain relative humidity and certain temperatures and in closed containers. This allows storage for up to a period of five years with virtually no change in quality. The present invention therefore also provides the use of compounds stored in such a way as catalysts for the production of polycarbonate by the melt interesterification process, particularly also without additional use of alkaline co-catalysts, such as sodium phenolate for example.
Phenol adducts of phosphonium phenolates wherein the phosphonium phenolate has the formula (I) are preferably stored 
where
R1 to R4 are the same or different and each stand for a C1-C12 alkyl, C5-C6 cycloalkyl, C7-C12 aryl alkyl or C6-C14 aryl radical preferably a C6-C14 aryl radical, particularly preferably for a C6 aryl radical, in particular a phenyl radical, and
R5 to R7 independently one of the others denote H, C1-C12 alkyl, C5-C6 cycloalkyl, C7-C12 aryl alkyl and C6-C14 aryl;
R5 to R7 particularly preferably denotes hydrogen
n denotes 1 or 2
particularly preferably 1,
and where n=2, R4 denotes a C2-C12 alkylene radical.
Formula (I) most preferably stands for tetraphenyl phosphonium phenolate.
According to the invention the phenol adducts of phosphonium phenolates, preferably the phenol adducts of tetraphenyl phosphonium phenolate, are stored as a crystalline solid, preferably as a free-flowing crystalline solid.
According to the invention the phenol adducts of phosphonium phenolates, preferably the phenol adducts of tetraphenyl phosphonium phenolate, are stored in closed metal, plastic or cardboard packages. They are preferably stored in steel or plastic containers with PE liners, which are packed under air, closed and sealed under a nitrogen atmosphere. They are particularly preferably stored in steel or plastic containers with PE liners, which are packed under atmospheric conditions, closed and sealed under a nitrogen atmosphere, of a size such that they may be used as a unit for preparing metering solutions without having to be split up.
According to the invention the phenol adducts of phosphonium phenolates, preferably the phenol adducts of tetraphenyl phosphonium phenolate, are stored at temperatures of xe2x88x9230 to 50xc2x0 C., preferably xe2x88x9220 to 40xc2x0 C. and particularly preferably 0 to 35xc2x0 C.
According to the invention the phenol adducts of phosphonium phenolates, preferably the phenol adducts of tetraphenyl phosphonium phenolate, are stored at a relative humidity of 30 to 70%, preferably 40 to 65%.
According to the invention the phenol adducts of phosphonium phenolates, preferably the phenol adducts of tetraphenyl phosphonium phenolate, may be stored for 0 to 5 years, preferably 0 to 3 years and particularly preferably 0 to 1.5 years.
The phenol adducts of phosphonium phenolates, preferably the phenol adducts of tetraphenyl phosphonium phenolate, stored according to the invention may be used in known ways as a catalyst for the production of polycarbonates (see for example U.S. Pat. No. 3,442,854). According to the melt interesterification process therein disclosed aromatic polycarbonates are produced for example from aromatic diphenols, carbonic acid diaryl esters and optionally branching agents and/or monophenols.
The phenol adducts of phosphonium phenolates, preferably the phenol adducts of tetraphenyl phosphonium phenolate, stored according to the invention are preferably used as a catalyst in the process described in DE-A 10 114 804 and in DE-A 10 119 851.
The phenol adducts of phosphonium phenolates, preferably the phenol adducts of tetraphenyl phosphonium phenolate, stored according to the invention may be used as interesterification catalysts in quantities of 10xe2x88x921 mol to 10xe2x88x928 mol, preferably in quantities of 10xe2x88x923 mol to 10xe2x88x927 mol, per mol of diphenol.
Further details of the melt interesterification process are described in the literature (see for example Hermann Schnell, Chemistry and Physics of Polycarbonates, Polymer Reviews, Vol. 9, 1964, pages 44 to 51, DE-B 1 031 512, U.S. Pat. Nos. 3,002,272, 3,022,272, 5,340,905 and 5,399,659, DE-A 10 119 851 and DE-A 10 114 804).
The thermoplastic polycarbonates produced with the phenol adducts of phosphonium phenolates, preferably the phenol adducts of tetraphenyl phosphonium phenolate, stored according to the invention are free from solvents and have a light inherent color.
The thermoplastic polycarbonates produced with the phenol adducts of phosphonium phenolates, preferably the phenol adducts of tetraphenyl phosphonium phenolate, stored according to the invention preferably correspond to the formula (II) 
wherein M denotes Ar or a defective structure A, B, C and/or D,
wherein the defective structure A 
xe2x80x83does not exceed
a content of 800 ppm
preferably 750 ppm
particularly preferably 500 ppm
xe2x80x83wherein the defective structure B 
xe2x80x83does not exceed
a content of 350 ppm
preferably 250 ppm
particularly preferably 70 ppm
wherein defective structure C 
xe2x80x83does not exceed
a content of 200 ppm
preferably 150 ppm
particularly preferably 60 ppm
wherein defective structure D 
xe2x80x83does not exceed
a content of 750 ppm
preferably 300 ppm
particularly preferably 150 ppm
wherein Y denotes H or 
xe2x80x83where R may be the same or different and may be H, C1-C20 alkyl, C6H5 and C(CH3)2C6H5, and n stands for 0, 1 or 2,
whereby X denotes Y or xe2x80x94(MOCOO)Y, and M and Y have the meanings described above,
where Ar denotes an aromatic radical with 6 to 30 C atoms, which may contain one or more aromatic nuclei, may be substituted and may contain aliphatic or cycloaliphatic radicals or alkyl aryls or heteroatoms as binding links
preferably a compound represented by formula (III) 
xe2x80x83or a compound represented by formula (IV) 
xe2x80x83where
E is C1-C8 alkylidene or C5-C12 cycloalkylidene, S, SO2 or a single bond, R is a substituted or unsubstituted phenyl, methyl, propyl, ethyl, butyl, Cl or Br and n stands for 0, 1 or 2,
and particularly preferably Ar represents the compounds according to the abov formula (IV).
The sum of all defective structures A to D should not exceed 1000 ppm, preferably 700 ppm, particularly preferably 550 ppm. The term ppm means ppm per weight, weight of defective structures in relation to the total weight of polycarbonate. This parameter is measured by complete hydrolysis of polycarbonate and separation of the xe2x80x9cdefectivexe2x80x9d compounds by HPLC.